US5899713A - Method of making NVRAM cell with planar control gate - Google Patents

Method of making NVRAM cell with planar control gate Download PDF

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Publication number
US5899713A
US5899713A US08/959,156 US95915697A US5899713A US 5899713 A US5899713 A US 5899713A US 95915697 A US95915697 A US 95915697A US 5899713 A US5899713 A US 5899713A
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gates
conductive layer
nvram
cmos
areas
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US08/959,156
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Joyce E. Molinelli Acocella
Randy W. Mann
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International Business Machines Corp
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International Business Machines Corp
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Assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION reassignment INTERNATIONAL BUSINESS MACHINES CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MOLINELLI ACOCELLA, JOYCE E., MANN, RANDY W.
Priority to KR1019980045417A priority patent/KR100275401B1/ko
Priority to US09/225,182 priority patent/US20020003254A1/en
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
    • H10B41/40—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the peripheral circuit region
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
    • H10B41/40—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the peripheral circuit region
    • H10B41/42—Simultaneous manufacture of periphery and memory cells
    • H10B41/43—Simultaneous manufacture of periphery and memory cells comprising only one type of peripheral transistor
    • H10B41/44—Simultaneous manufacture of periphery and memory cells comprising only one type of peripheral transistor with a control gate layer also being used as part of the peripheral transistor
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10B—ELECTRONIC MEMORY DEVICES
    • H10B41/00—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates
    • H10B41/40—Electrically erasable-and-programmable ROM [EEPROM] devices comprising floating gates characterised by the peripheral circuit region
    • H10B41/42—Simultaneous manufacture of periphery and memory cells
    • H10B41/49—Simultaneous manufacture of periphery and memory cells comprising different types of peripheral transistor

Definitions

  • the present invention relates generally to an NVRAM (nonvolatile random access memory) cell with a planar control gate, and more particularly pertains to an NVRAM cell with a planar control gate which is compatible with self-aligned silicide processes and also provides a planar surface for subsequent wiring processes.
  • NVRAM nonvolatile random access memory
  • Salicided processes do not work well, or work at all, when the polysilicon being silicided has a topography which includes large steps therein.
  • Salicided processes do not work with conventional NVRAM cells because of the severe topography created when the wordline poly passes over the floating gates.
  • the steps are large enough and steep enough to allow spacer formation on the top of the wordlines as they pass over the floating gate polysilicon. The spacer formation guarantees that silicide will not form continuously on the top of the wordline.
  • NVRAM cell with a planar control gate.
  • This type of structure is: 1) it is compatible with self-aligned silicide (salicide) processes; and 2) it provides a planar surface for subsequent wiring processes similar to a standard CMOS process without embedded NVRAM.
  • the technique for achieving this structure relies upon the CMP (chemical mechanical polishing) process. Large floating gate areas are defined with smaller areas cutout to isolate the individual memory cells. ONO is deposited on the floating gate areas, and a second poly layer is deposited thereon, or the ONO can be deposited first as described here and then the floating gate patterned.
  • the planar process of the present invention departs from a standard CMOS process at this point.
  • the second poly deposition is thicker for the planar process of the subject invention when compared to a standard CMOS process at this point, 320 nm vs 220 nm respectively. This thicker poly deposition is required to allow for poly removal during a subsequent planarization process. Resist shapes are patterned over the logic areas in the array where necessary according to a predetermined density algorithm. The second poly is reactive ion etched, followed by a chemical mechanical polishing (CMP) step to complete the planarization process. The final poly gate thickness is 200-220 nm in the logic areas and in the NVRAM control gate areas between floating gate regions, but only 100-120 nm for the control gate over the floating gate regions.
  • CMP chemical mechanical polishing
  • control gate physical thickness is decoupled (isolated) from the standard logic by standard photo-patterning and RIE etching processes, and the final structure of the CMOS logic device looks identical from a topological perspective to a standard CMOS structure.
  • the control gate of the NVRAM and the FET gate of the CMOS device are defined during this etch step.
  • An alternative process variation may involve a nitride mask incorporated in the logic areas to prevent dishing during the CMP step if this is a concern.
  • the present invention provides a method of fabricating mixed first and second type devices on a common substrate having a first type device region thereon and a second type device region thereon, wherein the first type device region is thicker than the second type device region.
  • a continuous conductive layer is formed over both the first type device region and the second type device region, to form first device gates, and second device gates.
  • the conductive layer is then planarized such that the conductive layer forming the first device gates is planar with the conductive layer forming the second device gates, and the conductive layer forming the second device gates is thicker than the conductive layer forming the first device gates.
  • the substrate has a first NVRAM region thereon and a second CMOS region thereon, and a layer of polysilicon is deposited for formation of the NVRAM control gates and the CMOS gates.
  • a planarizing operation the upper surface of the resulting CMOS gates surfaces is planar with the upper surface of the NVRAM control gates, and the conductive layer forming the CMOS gates is thicker than the conductive layer forming the NVRAM gates over floating gate regions.
  • the planarizing step preferably comprises reactive ion etching of the conductive layer through a mask, followed by chemical mechanical polishing of the conductive layer.
  • a metal layer is deposited and a silicide is formed.
  • a metal layer is deposited, a silicide is formed on the planarized surface, followed by patterning to form discrete control gates.
  • the present invention also provides a semiconductor device comprising a planar substrate having thereon a first multilayer device having an upper conductive layer and a second multilayer device having an upper conductive layer.
  • the second multilayer device has a different number of layers than the first multilayer device, and the upper conductive layers of the first and second multilayer devices have planarized coplanar top conductive surfaces.
  • the first multilayer device comprises a control gate over a floating gate for an NVRAM memory cell
  • the second multilayer device comprises a gate of an FET
  • the upper conductive layer of the first multilayer device is thinner than the upper conductive layer of the second multilayer device.
  • the first multilayer device includes a layer of polysilicon for NVRAM control gates
  • the second multilayer device includes a layer of polysilicon for CMOS FET gates.
  • FIG. 1 illustrates a portion of a semiconductor chip, which is primarily a CMOS (complementary-metal-oxide semiconductor) chip having areas of NVRAM (nonvolatile random access memory) formed therein.
  • CMOS complementary-metal-oxide semiconductor
  • NVRAM nonvolatile random access memory
  • FIG. 2 illustrates the structure of FIG. 1 having a second polysilicon layer deposited thereon to eventually form control gates and logic devices on the semiconductor chip.
  • FIG. 3 illustrates the structure of FIG. 2 having resist shapes patterned over the logic areas and in the array where necessary to form a mask to enable the poly to be directionally reactive ion etched through the openings in the resist mask to remove the major topographical humps in the top of the poly.
  • FIG. 4 illustrates the different thicknesses of the poly remaining over the NVRAM floating gates, which form the control gates therefor, and the poly remaining over the CMOS gates, after a chemical mechanical polishing operation which provides a planar upper surface for the poly.
  • FIGS. 5 and 6 illustrate the structure of FIG. 4 after the poly and salicided metal layer are patterned with normal processing, with FIG. 5 being in the same direction as FIG. 4 and FIG. 6 being rotated 90° with respect to FIGS. 4 and 5.
  • FIG. 1 illustrates a portion of a semiconductor chip, which contains both CMOS (complementary-metal-oxide semiconductor) areas and NVRAM (nonvolatile random access memory) areas formed or embedded therein.
  • the semiconductor chip is formed on a substrate 10 having a plurality of STI (shallow trench isolation) oxide isolation regions 12 formed therein, and a layer of tunnel oxide 14 and CMOS gate oxide 22 formed on the silicon surface.
  • STI shallow trench isolation
  • the NVRAM area of the chip includes a plurality of floating gates 16 formed from a first layer of polysilicon deposited thereon, each of which has a height of approximately 1000 ⁇ . This height can vary depending on the specific integration needs, 1000 ⁇ 500 ⁇ is a reasonable range.
  • Each floating gate has a layer of ONO (oxide-nitride-oxide) 18 deposited on the top of the first layer of poly, and oxide regions grown on the sides thereof(not shown).
  • ONO oxide-nitride-oxide
  • the CMOS area of the chip includes a plurality of CMOS oxide gates 22 formed thereon, only one of which is illustrated with an exaggerated height in FIG. 1.
  • FIG. 2 illustrates the structure of FIG. 1 having a second polysilicon layer 24 deposited thereon in a blanket manner over the memory cells, the isolation regions and the CMOS regions.
  • the second poly layer eventually forms control gates and CMOS logic device gates on the semiconductor chip.
  • the second polysilicon layer 24 is slightly thicker (500-1000 ⁇ thickness) for optimization of the planarization process as described herein when compared to a more standard prevalent prior art thickness, 320 nm vs 220 nm respectively.
  • the thicker layer of poly is required to allow for poly removal during a subsequent planarization process.
  • the second poly layer 24 is deposited conformally over the structure of FIG. 1, as illustrated in FIG. 2, such that the upper surface thereof conforms generally to the structure on the chip on which the polysilicon layer is deposited.
  • FIG. 3 illustrates the structure of FIG. 2 having resist shapes 26 patterned over the logic areas and in the array where necessary according to the predetermined density algorithm.
  • the resist shapes form a mask to enable the poly to be directionally RIE'd (reactive ion etched) through the openings in the resist mask to remove the major topographical humps in the top of the poly, as shown in FIG. 3.
  • the RIE operation is followed by a CMP (chemical mechanical polishing) operation to smooth the top of the poly, to achieve the structure shown in FIG. 4.
  • CMP chemical mechanical polishing
  • the final poly gate thickness is 200-220 nm (2000 ⁇ ) in the CMOS logic areas and in the NVRAM control gate areas between floating gate regions, but only 100-120 nm (1200 ⁇ ) for the control gates over the floating gates.
  • the control gate physical thickness is then decoupled or isolated from the standard logic by standard photo-patterning, RIE etching and silicide formation processes, and the final structure looks identical from a topological perspective to a standard CMOS structure. It is noted that a nitride mask can be incorporated in the logic area to prevent dishing during the CMP step if this is a concern.
  • FIG. 4 illustrates the different thicknesses of the poly remaining over the NVRAM floating gates, which form the control gates, and the poly remaining over the CMOS gates and between NVRAM floating gates, after the CMP operation which provides a planar upper surface for the poly.
  • the gates are patterned and etched, decoupling the CMOS regions from the NVRAM regions. This step also completes the definition of the control gate poly over the floating gate regions, as shown in FIG. 5.
  • the side wall spacers are then formed by blanket deposition and RIE, followed by the necessary implants and anneal steps.
  • a blanket metal layer 28 consisting of Ti or Co is deposited thereon, for a salicide operation thereon to produce low resistance wordlines and gates on the chip.
  • Silicide is also formed on source and drain regions during this step.
  • An option is to deposit a metal or form silicide on top of the gates before the gate patterning RIE, followed by formation of silicide on the source/drain regions after the gate patterning RIE, as is known in the industry.
  • FIG. 5 illustrates the structure of FIG. 4 after the poly and salicided metal layer 30 are patterned with normal processing techniques to produce the control gates over the floating gates and between floating gates in the NVRAM portions of the chip and the control gates in the CMOS (FET) portions of the chip.
  • FET CMOS
  • FIG. 6 illustrates the structure of FIG. 5 rotated 90° with respect to the view of FIG. 5.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Semiconductor Memories (AREA)
US08/959,156 1997-10-28 1997-10-28 Method of making NVRAM cell with planar control gate Expired - Fee Related US5899713A (en)

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US08/959,156 US5899713A (en) 1997-10-28 1997-10-28 Method of making NVRAM cell with planar control gate
KR1019980045417A KR100275401B1 (ko) 1997-10-28 1998-10-28 반도체 디바이스 및 그 제조 방법
US09/225,182 US20020003254A1 (en) 1997-10-28 1999-01-04 Nvram cell with planar control gate

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6426237B2 (en) 1998-12-18 2002-07-30 Eastman Kodak Company Method for producing optically planar surfaces for micro-electromechanical system devices
EP1363324A1 (en) * 2002-05-16 2003-11-19 STMicroelectronics S.r.l. Method for manufacturing non-volatile memory device
US20040011325A1 (en) * 2000-05-04 2004-01-22 Benson Donald J. System for estimating auxiliary-injected fueling quantities
KR100487410B1 (ko) * 2000-07-22 2005-05-03 매그나칩 반도체 유한회사 반도체 소자의 제조방법
US20050185446A1 (en) * 2004-02-24 2005-08-25 Luca Pividori Method for reducing non-uniformity or topography variation between an array and circuitry in a process for manufacturing semiconductor integrated non-volatile memory devices
WO2009016437A1 (en) * 2007-08-01 2009-02-05 Freescale Semiconductor, Inc. Method of manufacturing a semiconductor device and semiconductor device obtainable therewith
US20100052034A1 (en) * 2008-08-26 2010-03-04 International Business Machines Corporation Flash memory gate structure for widened lithography window
US20120056260A1 (en) * 2009-02-13 2012-03-08 Spansion Llc Method and device employing polysilicon scaling
US20130049074A1 (en) * 2011-08-23 2013-02-28 Micron Technology, Inc. Methods for forming connections to a memory array and periphery

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009088060A (ja) * 2007-09-28 2009-04-23 Nec Electronics Corp 不揮発性半導体記憶装置及びその製造方法
JP5184851B2 (ja) * 2007-09-28 2013-04-17 ルネサスエレクトロニクス株式会社 不揮発性半導体記憶装置の製造方法

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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6426237B2 (en) 1998-12-18 2002-07-30 Eastman Kodak Company Method for producing optically planar surfaces for micro-electromechanical system devices
US20040011325A1 (en) * 2000-05-04 2004-01-22 Benson Donald J. System for estimating auxiliary-injected fueling quantities
KR100487410B1 (ko) * 2000-07-22 2005-05-03 매그나칩 반도체 유한회사 반도체 소자의 제조방법
EP1363324A1 (en) * 2002-05-16 2003-11-19 STMicroelectronics S.r.l. Method for manufacturing non-volatile memory device
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US20050185446A1 (en) * 2004-02-24 2005-08-25 Luca Pividori Method for reducing non-uniformity or topography variation between an array and circuitry in a process for manufacturing semiconductor integrated non-volatile memory devices
WO2009016437A1 (en) * 2007-08-01 2009-02-05 Freescale Semiconductor, Inc. Method of manufacturing a semiconductor device and semiconductor device obtainable therewith
US20100227467A1 (en) * 2007-08-01 2010-09-09 Freescale Semiconductor, Inc. Method of manufacturing a semiconductor device and semiconductor device obtainable therewith
US8043951B2 (en) 2007-08-01 2011-10-25 Freescale Semiconductor, Inc. Method of manufacturing a semiconductor device and semiconductor device obtainable therewith
US20100052034A1 (en) * 2008-08-26 2010-03-04 International Business Machines Corporation Flash memory gate structure for widened lithography window
US7888729B2 (en) 2008-08-26 2011-02-15 International Business Machines Corporation Flash memory gate structure for widened lithography window
US20120056260A1 (en) * 2009-02-13 2012-03-08 Spansion Llc Method and device employing polysilicon scaling
US8637918B2 (en) * 2009-02-13 2014-01-28 Spansion Llc Method and device employing polysilicon scaling
US20130049074A1 (en) * 2011-08-23 2013-02-28 Micron Technology, Inc. Methods for forming connections to a memory array and periphery

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US20020003254A1 (en) 2002-01-10
KR19990037455A (ko) 1999-05-25
KR100275401B1 (ko) 2000-12-15

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